The Signature of Snow

The history of the planet can be found inside a sediment core at the bottom of the ocean, or the cake-like layers of a soil pit, or in the strata of the Grand Canyon. So it shouldn’t be too surprising that the climatic history of water — and a hint about its future — can sometimes be found by digging into a pit of snow.

“Snowpack does have a stratigraphy when you dig those pits,” said Katherine Markovich, whose graduate research at UC Davis and with UC Water took her to the mountains of Chile. Her work there, along with fellow graduate students Stephen Maples and Lauren Foster, is chronicled in a video from UCTV Sustainable California called “Water’s Signature.”

Mediterranean climates like Chile and California are changing. Precipitation that has long fallen as snow is increasingly falling as rain. What does that mean for the water supply below, and how can we prepare for it? Where will the water go without the snow?

This graphic shows how warmer temperatures will melt snowpack more quickly and dump more rain and less snow on mountain ranges, leading to increased flood risk. (California Department of Water Resources)

Hydrologic detective

To sift through those questions, Markovich said she got to play “hydrologic detective,” looking for clues in the snowpack and streams to find out where the water has come from and where it might be expected to go in a hotter, drier future.

By digging through snow pits and taking water samples from mountain streams, the team identified the isotopic signatures of the snow and water. Those tell-tale signatures let them back-calculate to determine what portion of the water in the streams came from snowmelt, rain or groundwater. Her next step is to model that information forward to help predict where and how much water may flow in the future.

“We need to be talking about the snowpack and how climate change will impact it.” — Katherine Markovich

Her research shows that it is not enough to just quantify the snowpack and water availability but to also look at the subsurface, which includes groundwater but also those in-between flow pathways in unsaturated zones. Markovich said this zone is highly sensitive to climate change because if it is drier than in past years, it will impact the movement of water from precipitation to streamflow.

“We need to be talking about the snowpack and how climate change will impact it,” said Markovich, now a postdoctoral fellow at the University of Arizona. “My research shows you need to holistically characterize the mountain system to predict our water availability in the future.”

Chile does not rely on the many dams and reservoirs that make up California’s water system, which in some ways gives it more flexibility to plan with climate change in mind.

“I think California can provide a lot of guidance in terms of what to do and what not to do for other places that are starting to experience water supply and reliability issues,” Maples said.